code: def _train_feature(ctx, params, model, fc):
      for epoch in range(params.iter_count):
          rmse = _feature_loop(ctx, params, model, fc)
  
      return rmse
  
imports: import logging
  import time
  import pandas
  import numpy
  import numba
  from seedbank import numpy_rng
  from .bias import Bias
  from .mf_common import MFPredictor
  from ..None import util
label_desc: Use image node_id 4 for calling a global function with example usage: _train_feature(ctx, params, model, fc) and returns: rmse